The longest we have ever stayed was 9 nights, last year and this year. This year, it was supposed to be 10 nights, but I wasn't feeling well, and we left a day early.
Next year will be the first trip for our daughter and the first trip since having kids, that we won't have a kid back at home with grandma. So we'll be staying a little longer, without having to feel rushed to get back home to our child. But even so, we will still only be there 12 nights...2 nights at the Nickelodean Suites, 5 nights at the Polynesian and 5 at the Beach Club. I really have no desire to be there much longer than that. Possibly a full two weeks, but even that would be pushing it. So I would say no longer than two weeks. And this includes off property days, like a day at Sea World, the Beach, shopping, etc.